Unveiling the potential of intranasal delivery of renin-angiotensin system drugs: Insights on the pharmacokinetics of irbesartan.

The therapeutic interest of renin-angiotensin system (RAS) drugs for the treatment of neuroinflammation has been recently acknowledged. Nevertheless, most of them display limited passage across the blood-brain barrier (BBB). Therefore, this study investigated the potential of intranasal (IN) delivery of six RAS drugs to circumvent the BBB and attain the brain, envisioning its future use in central nervous system (CNS) neuroinflammatory diseases, such as Alzheimer's disease (AD). Captopril, enalaprilat, irbesartan, lisinopril, losartan and valsartan were firstly screened based on their impact on the viability of nasal, lung, and neuronal cell lines and their apparent permeability (P_app) across porcine olfactory mucosa. Irbesartan, identified as the one with the best safety and permeability balance, was selected for pharmacokinetic characterization following single and multidose IN administration to CD-1 mice. The results were compared to those obtained by intravenous (IV) injection to assess direct nose-to-brain drug delivery. Olfactory toxicity and anxiety were also evaluated after multidose IN treatment. Irbesartan IN administration significantly enhanced brain targeting, with a 3-fold increase in the maximum concentration (C_max) and a 2.5-fold increase in the area under the curve (AUC_t) in the brain compared to IV route. The drug exhibited a t_max of 15 min post-IN administration and achieved a brain targeting efficiency of 239.56%, with a significant direct transport percentage of 58.26%. Multidose administration indicated no systemic or tissue accumulation, with accumulation ratio (R_ac) values below 1.0, and no significant olfactory toxicity. Overall, the study highlights the potential of IN delivery of irbesartan as a promising strategy to improve brain targeting and therapeutic outcomes in CNS diseases such as AD, providing an effective approach to bypass BBB limitations.